Bore machining method and apparatus

ABSTRACT

A method of machining the internal bore of a hollow pipe comprises honing material from inner surface of the bore the pipe. A honing apparatus for use in the method comprises a machining tool comprising a honing head adapted for insertion into the end of a pipe to remove material from the inner surface of the pipe by abrasion.

This invention relates to a method and apparatus for machining a bore and more particularly to a method and apparatus for machining a bore in a pipe, most specifically an internal bore running longitudinally through a pipe.

In the transportation of fluids, and particularly hydrocarbons such as oil and gas, extensive pipelines are created to carry the fluids for example from the point of recovery which may be many hundreds of miles off-shore, to onshore processing facilities or to end users. The pipelines are formed from individual pipe sections which are joined end to end to cover the required distance.

One established method for joining pipe sections together is to create a weld between the end of one pipe and the end of the next pipe. Such girth welds are commonly employed in the construction of fatigue sensitive deepwater pipelines or riser systems for oil and gas recovery.

When a pipeline is being laid, a number of pipe sections are gathered together and each pipe is offered up to the end of the pipeline and welded into position. The individual pipe sections may have been manufactured using a variety of different forming methods and therefore, although the pipe sections may have the same general outer diameter and length, they may exhibit variations in eccentricity of the inner diameter relative to the outer diameter, wall thickness and circularity.

Variations in the pipe dimensions can lead to internal off-sets between the surface of two adjoining pipes which can increase the stress concentration factor and therefore reduce the fatigue performance and fracture resistance of the weld and also increase the likelihood of forming weld defects in the root of the weld.

Additionally, any off-set in the internal dimensions of the pipes can make matching of further components such as end fittings and collars, i.e. J-lay collars difficult as these components are generally formed with standard dimensions in order to fit a range of pipes manufactured by different methods.

At present, any off set in the internal bores of adjoining pipe ends is machined using a lathe and more generally a computer numerical controlled lathe. These machines are generally very bulky and the pipe must be clamped securely within the lathe to prevent movement during machining. The lathe is rigidly mounted to reduce vibration which may adversely affect the surface finish and increase tool wear. Furthermore, these machines require a high level of operator skill in order to accurately machine the inner bore of the pipe which makes replication of the machining operation difficult.

It is therefore an object of the present invention to provide a method of machining the bore of a hollow tubular member, and more specifically the internal bore of a pipe which improves the consistency of each pipe to be laid in a pipeline.

It is a further object of the present invention to provide an apparatus for machining a bore in a pipe which addresses the above discussed problems and overcomes or at least mitigates these problems.

According to one aspect of the present invention there is provided a method a machining the internal bore of a hollow pipe, the method comprising honing material from the inner surface of the bore of the pipe.

Preferably a machining tool comprising a honing head is inserted into the end of the pipe and operated to hone material from the inner surface of the pipe.

Honing of material from the inner bore of the pipe is carried out by inserting a machining tool comprising a honing head into the end of the pipe and as such only light clamping of the machining tool to the pipe is required rather than secure clamping as with known methods using lathes as described above. This is particularly advantageous in relation to fatigue sensitive deepwater pipelines and riser systems as high clamping forces applied to the pipe can lead to risk of surface damage to the steel or any coating in the area of the clamps. Furthermore, clamping of the lathe in the region of the pipe end can lead to damage of the pipe end and therefore offsets between the ends of two pipes. The present invention avoids such problems as there is no requirement for secure clamping of the honing head to the pipe.

Advantageously, the effective diameter of the honing head is adjusted to control the amount of material removed from the inner surface of the pipe.

Preferably the position of the machining tool is adjusted before insertion into the end of the pipe. The original centreline and adjusted centreline are determined using a laser and suitable calculation software.

Advantageously the centre of the pipe is calculated via a laser metrology system. Conveniently the position of the machining tool is adjusted such that the centre of the machining tool matches the calculated centre of the pipe.

According to a further aspect of the present invention there is provided an apparatus for use in the method of the first aspect of the present invention, the apparatus comprising a machining tool comprising a honing head adapted for insertion into the end of a pipe to remove material from the inner surface of the pipe by abrasion.

Preferably one or more abrasive stones are mounted on the honing head. Advantageously the stones are mounted on the end of arms which are adjustably mounted on the honing head. Preferably the arms are telescopically or pivotally mounted on the honing head such that the outer diameter of the honing head can be adjusted by adjusting the position of the arms relative to the body of the honing head.

Preferably the honing head is concentric with the pipe being machined. Alternatively the honing head may be eccentric with the pipe. Advantageously, the relative position of the honing head with respect to the axis of the pipe is adjustable. This enables the operator to to offset the head to deal with eccentricity or to preserve the minimum wall thickness. The stones of the honing head may comprise bars mounted on the outer surface of the honing head. The length of the stones may be adjustable in order to adjust the amount of material removed from the inner surface of the pipe during a honing operation. Alternatively the stones are rotatably mounted to the arms.

Preferably, the machining tool is mounted within a housing from which it can be withdrawn for use. Preferably the machining tool comprises an actuator means for advancing the machining tool within and subsequently out of the housing. Advantageously the housing is mounted on a position adjustable cradle such that the housing can be repositioned horizontally and/or vertically with respect to the end of a pipe to be machined.

Conveniently the apparatus further comprises a laser metrology system for scanning the end of a pipe to calculate the centre of the pipe.

According to a further aspect of the present invention there is provided a method of joining two tubular members in a pipeline characterised in that the method includes the step of honing material from the internal bore on each of the tubular member to eliminate internal offsets between the tubular members to be joined.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which:

FIG. 1 is a schematic part cross sectional view of an apparatus according to one aspect of the present invention;

FIG. 2 is a perspective view of a self contained honing machine which forms part of the apparatus of FIG. 1;

FIG. 3 is an end view of a pipe with the honing machine in use;

FIG. 4 is a schematic part cross sectional view of an apparatus according to a further aspect of the present invention;

FIG. 5 is a schematic view of a drive shaft and support bearings of an apparatus of FIG. 4, and

FIG. 6 is a close up view of the honing bars of the apparatus of FIG. 4.

Turning now to the Figures there is shown in FIG. 1 a horizontal honing apparatus 1 according to one aspect of the present invention for machining a bore 2 in a tubular member 3 such as a pipe. The honing apparatus comprises a machining tool 4 which comprises a body 5. One or more honing members 6, which are preferably abrasive stones, are mounted around the outer circumference of the body. The honing members may be equi-spaced around the body or may be grouped together around the body at selected locations.

In the preferred embodiment, the honing members 6 are mounted upon extendible arms 7 which are fixed to the outer surface of the body 5. The arms may comprise rams 8 such as hydraulic or pneumatic rams, the position of which can be extended radially from the body to increase the distance between the honing members and the outer surface of the body. In the embodiment shown there are eight honing members mounted upon eight extendible arms around the outer surface of the body.

The honing members are preferably abrasive stones and in the embodiment shown, each honing member comprises a disc 9 rotatably mounted on the end of an extendible arm. The honing stones may comprise abrasive ceramic materials with composition and particle size regulated to give varying degrees of metal removal and desired surface finish.

The machining tool is mounted within a hollow, tubular housing 10 which is accurately machined to provide a smooth clamping surface 11 for a clamping module 12 of the machining tool which securely positions the honing tool within the housing. The clamping module comprises a ring 13 around the outer surface of the body. A plurality of brace members 14 extend from the ring and function to hold the body clear of the hollow tubular housing and also to centralise the body within the hollow tubular housing.

An actuating member 15 is mounted to the body on the trailing edge 16 (in use) of the body. In this embodiment the actuating member is a rod 17 which extends substantially from the centre of the trailing face of the body.

A control umbilical 18 is connected to the body for transmitting power to the body. The control umbilical preferably passes through the actuating member and connects to the trailing surface of the body to avoid the umbilical becoming trapped during use between the body and the housing which could affect the performance of the apparatus.

Positing means 19 are provided for altering the position of the tubular housing horizontally and vertically with respect to a pipe within which the machining tool is intended to operate. The positioning means comprises a cradle 20 within which the tubular housing is received or upon which it is supported. In the embodiment shown, the cradle comprises a substantially horizontal platform 21 mounted upon one or more pairs of substantially vertical legs. A pair of legs 22 is provided at or near the forward end of the positioning means, the legs extending across the underside of the platform one in front of the other to provide a space therebetween.

A further set of legs 23 depend from a surface above the platform.

The positioning means further comprises means (not shown) for altering the height of the cradle. These may for example be hydraulic or pneumatic means. The positioning means preferably also comprise control means to enable a user to control the positioning of the cradle.

Guide members 24 extend from the outer surface of the tubular housing which co-operate with the legs of the positioning means. The guide members comprise blocks or bars which slide within the space between the pairs of legs 22,23 as the cradle is raised or lowered.

A faceplate 25 is mounted on the leading edge of the tubular housing to facilitate mounting of a known laser metrology system such as a manual pipechecker tool available from Optical Metrology Services Ltd.

The faceplate is accurately machined and positioned such that the centre of the faceplate and that of the machining tool are common when the tool is in position within the housing.

A roller 26 is mounted at the end of the cradle, remote from the faceplate to guide the umbilical 18 of the positioning rod and to prevent the umbilical from becoming snagged on the end of the cradle.

In use of the apparatus, the machining tool 4 is mounted within the tubular housing 10 and a pipe 3 to be machined is placed on a support surface or working platform with the end of the pipe facing the open end of the housing. The separation of the end of the pipe and the faceplate 25 of the apparatus is minimised in order to minimise overhang of the machining tool during operation as much as possible thereby avoiding the need for support rollers or legs ahead of the apparatus.

The laser metrology system is operated to scan the pipe end and determine a new theoretical centre. The cradle 20 of the apparatus is then repositioned such that the centre of the machining tool 4 is aligned with the new theoretical centre of the pipe. The cradle may be aligned manually or may be controlled by an operator via the control means described above. Alternatively the cradle may be remotely controlled.

Following repositioning of the apparatus the extending arms 7 of the machining tool are set to the required distance from the body of the machining tool and the machining tool is operated to rotate the honing members 6 around the body of the tool. The machining tool is then advanced through the tubular housing 10 by applying a force on the actuating member 17 to push the tool from the housing and into the end of the pipe.

As the honing members 6 come into contact with the inner surface of the pipe 2, material from the surface is removed. By setting the maximum radial displacement of the arms it is possible to machine a true circle of a specified diameter.

After completion of the honing operation, the tool 4 is pulled back into the tubular housing via the actuating member 17 where the extension of the arms 7 can be reset or the honing members replaced or repaired.

After machining a further laser scan is performed as a quality control check and to provide a permanent record of the operation. If required, the operation can be repeated.

A further embodiment of the present invention is illustrated in FIGS. 4-6. In this embodiment, the machining tool 30 comprises a honing head 31 mounted on one end of a drive shaft or spindle 32. The other end of the drive shaft is connected to a drive motor 33. One or more guide bearings 34 are provided which support the drive shaft between the motor and the honing head. In this embodiment, the drive motor and guide bearings are mounted on an adjustable cradle or table 35, the position of which can be adjusted in the X, Y and Z directions so as to align the honing head with the end of a pipe mounted on a support member adjacent the adjustable table.

In this embodiment the honing head 31 comprises a cylindrical body 36 with a plurality of honing bars 37 mounted on the outer surface of the body. The bars are preferably aligned with the longitudinal axis of the body of the head.

A laser metrology system (not shown) as described above in relation to the first embodiment is mounted on the honing apparatus or in a suitable location for scanning of a pipe end 38.

In use of this embodiment, after scanning of the pipe end, the adjustable table 35 is repositioned such that the centre of the honing head 31 is aligned with the new centre position of the pipe. The adjustable table can then be advanced towards the pipe such that the honing head is advanced into the end of the pipe. Alternatively, the support member upon which the pipe is mounted is advanced towards the machining apparatus.

The motor 33 is activated and the honing head is rotated within the pipe end 38 such that the honing bars 37 come into contact with the inner surface of the pipe and remove material from the inner surface to correct any ovality or variation in the inner diameter.

Following completion of the honing operation, the adjustable table is withdrawn such that the honing head is withdrawn from the end of the pipe. Alternatively, the support member is moved away from the adjustable table to achieve the same result.

The length of the honing bars 37 may be selected to allow removal of a desired length of material from the inner surface of the end of the pipe in one or more stages. Furthermore, the shape of the honing bars may be selected to provide different profiles, i.e. parallel or tapered and or with a radius at the end to transition to the un-machined area.

The present invention is particularly advantageous in that due to the low reaction forces between the machining tool and the pipe, only light clamping of the pipe is necessary. Furthermore, the low forces mean that the machining tool itself need not clamp directly onto the pipe being machined. This allows the apparatus to be more portable than is currently possible such that the apparatus can be moved from location to location to machine pipes in situ on a pipe laying barge for example prior to the pipes being laid.

The method can be applied to pipes from a variety of manufacturing methods such as seamless, welded or extruded and a variety of material types such as but not limited to solid or internally CRA clad forms. A primary application is for seamless pipe typically in the size range of 6 inches to 16 inches outer diameter. Seamless pipes are particularly subject to dimensional variations in the form of eccentricity and out of roundness.

The present invention allows for machining of pipes without the need for complex programming or operator adjustments as the honing members can be pre-formed to shape for example with a radius or taper at the end to transition from the machined to the non-machined area.

Modifications and/or alterations to the features described above are envisaged such as measurement and adjustment of the centreline may be performed by a manual or automated means although preferably an automated means is used for speed and accuracy. Prior to carrying out the machining operation, the suitability of the pipe end may be determined by checking that the minimum allowable wall thickness will be maintained after machining. This check may be an in-built function of the control software.

The honing head is generally concentric with the original pipe or tube. However, the head may be eccentric to the natural axis of the pipe at the beginning of the operation and consequently the head may require to be supported sufficiently to resist lateral loads placed on the head.

The honing members of the honing head may be displaced radially by the centrifugal force generated during rotation of the honing head.

The apparatus may be used to machine the bore of a pipe along the entire length of the pipe or only used at the extremity of the pipe as described above. 

1. A method of machining the internal bore of a hollow pipe, the method comprising: honing material from the inner surface of the bore of the pipe.
 2. A method according to claim 1, comprising the step of inserting a machining tool comprising a honing head into the end of the pipe to hone material from the inner surface of the pipe.
 3. A method according to claim 1 comprising the step of adjusting the effective diameter of the honing head to control the amount of material removed from the inner surface of the pipe.
 4. A method according to claim 1, further comprising the step of adjusting the position of the machining before insertion into the end of the pipe.
 5. A method according to claim 4, wherein the original centreline and adjusted centreline are determined using a laser and calculation software.
 6. A method according to claim 5, wherein the centre of the pipe is calculated via a laser metrology system.
 7. A method according to claim 5, wherein the position of the machining tool is adjusted such that the centre of the machining tool matches the calculated centre of the pipe.
 8. A method according to claim 1, wherein the honing head is mounted concentrically within the pipe being machined.
 9. A method according to claim 1, wherein the honing head is mounted eccentrically within the pipe.
 10. (canceled)
 11. A honing apparatus for use in the method of claim 1, the apparatus comprising: a machining tool comprising a honing head adapted for insertion into the end of a pipe to remove material from the inner surface of the pipe by abrasion.
 12. An apparatus according to claim 11, wherein one or more abrasive stones are mounted on the honing head.
 13. An apparatus according to claim 12, wherein the stones are mounted on the end of arms which are adjustably mounted on the honing head.
 14. An apparatus according to claim 13, wherein the arms are telescopically or pivotally mounted on the honing head such that the outer diameter of the honing head can be adjusted by adjusting the position of the arms relative to the body of the honing head.
 15. An apparatus according to claim 13, wherein the stones are rotatably mounted to the arms.
 16. An apparatus according to claim 12, wherein the stones of the honing head comprise bars mounted on the outer surface of the honing head.
 17. An apparatus according to claim 12, wherein the length of the stones is adjustable in order to adjust the amount of material removed from the inner surface of the pipe during a honing operation.
 18. An apparatus according to claim 11, wherein the apparatus comprises a housing within which the machining tool is mounted and from which it can be withdrawn for use.
 19. An apparatus according to claim 18, wherein the machining tool comprises an actuator means for advancing the machining tool within and subsequently out of the housing.
 20. An apparatus according to claim 18, wherein the apparatus further comprises a position adjustable cradle upon which the housing is mounted such that the housing can be repositioned horizontally and/or vertically with respect to the end of a pipe to be machined.
 21. An apparatus according to claim 11, wherein the apparatus further comprises a laser metrology system for scanning the end of a pipe to calculate the centre of the pipe.
 22. (canceled)
 23. A method of joining two tubular members in a pipeline, wherein the method includes the step of honing material from the internal bore on each of the tubular member according to claim 1 to eliminate internal offsets between the tubular members to be joined.
 24. (canceled) 